Add "Best Book Move" UCI option

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index cd874ff816156bfcfd036c65de3443a917325341..0e65d19ff3c9f5d8da2d9fd7887ceb2bb42ec3e5 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -232,7 +232,7 @@ namespace {
   const Value EasyMoveMargin = Value(0x200);
 
   // Last seconds noise filtering (LSN)
-  const bool UseLSNFiltering = false;
+  const bool UseLSNFiltering = true;
   const int LSNTime = 4000; // In milliseconds
   const Value LSNValue = value_from_centipawns(200);
   bool loseOnTime = false;
@@ -257,7 +257,7 @@ namespace {
   int SearchStartTime, MaxNodes, MaxDepth, MaxSearchTime;
   int AbsoluteMaxSearchTime, ExtraSearchTime, ExactMaxTime;
   bool UseTimeManagement, InfiniteSearch, PonderSearch, StopOnPonderhit;
-  bool FirstRootMove, AbortSearch, Quit, AspirationFailLow;
+  bool FirstRootMove, AbortSearch, Quit, AspirationFailLow, ZugDetection;
 
   // Log file
   bool UseLogFile;
@@ -294,7 +294,7 @@ namespace {
   Depth extension(const Position&, Move, bool, bool, bool, bool, bool, bool*);
   bool ok_to_do_nullmove(const Position& pos);
   bool ok_to_prune(const Position& pos, Move m, Move threat);
-  bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply);
+  bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply, bool allowNullmove);
   Value refine_eval(const TTEntry* tte, Value defaultEval, int ply);
   void update_history(const Position& pos, Move move, Depth depth, Move movesSearched[], int moveCount);
   void update_killers(Move m, SearchStack& ss);
@@ -387,7 +387,7 @@ bool think(const Position& pos, bool infinite, bool ponder, int side_to_move,
       if (get_option_value_string("Book File") != OpeningBook.file_name())
           OpeningBook.open(get_option_value_string("Book File"));
 
-      Move bookMove = OpeningBook.get_move(pos);
+      Move bookMove = OpeningBook.get_move(pos, get_option_value_bool("Best Book Move"));
       if (bookMove != MOVE_NONE)
       {
           if (PonderSearch)
@@ -425,6 +425,7 @@ bool think(const Position& pos, bool infinite, bool ponder, int side_to_move,
   MultiPV                 = get_option_value_int("MultiPV");
   Chess960                = get_option_value_bool("UCI_Chess960");
   UseLogFile              = get_option_value_bool("Use Search Log");
+  ZugDetection            = get_option_value_bool("Zugzwang detection"); // To be removed after 1.7.1
 
   if (UseLogFile)
       LogFile.open(get_option_value_string("Search Log Filename").c_str(), std::ios::out | std::ios::app);
@@ -1299,7 +1300,7 @@ namespace {
     tte = TT.retrieve(posKey);
     ttMove = (tte ? tte->move() : MOVE_NONE);
 
-    if (tte && ok_to_use_TT(tte, depth, beta, ply))
+    if (tte && ok_to_use_TT(tte, depth, beta, ply, allowNullmove))
     {
         ss[ply].currentMove = ttMove; // Can be MOVE_NONE
         return value_from_tt(tte->value(), ply);
@@ -1625,7 +1626,7 @@ namespace {
     tte = TT.retrieve(pos.get_key());
     ttMove = (tte ? tte->move() : MOVE_NONE);
 
-    if (!pvNode && tte && ok_to_use_TT(tte, depth, beta, ply))
+    if (!pvNode && tte && ok_to_use_TT(tte, depth, beta, ply, true))
     {
         assert(tte->type() != VALUE_TYPE_EVAL);
 
@@ -1712,7 +1713,7 @@ namespace {
 
       // Detect blocking evasions that are candidate to be pruned
       evasionPrunable =   isCheck
-                       && bestValue != -VALUE_INFINITE
+                       && bestValue > value_mated_in(PLY_MAX)
                        && !pos.move_is_capture(move)
                        && pos.type_of_piece_on(move_from(move)) != KING
                        && !pos.can_castle(pos.side_to_move());
@@ -2306,14 +2307,18 @@ namespace {
   }
 
 
-  // ok_to_use_TT() returns true if a transposition table score
-  // can be used at a given point in search.
+  // ok_to_use_TT() returns true if a transposition table score can be used at a
+  // given point in search. To avoid zugzwang issues TT cutoffs at the root node
+  // of a null move verification search are not allowed if the TT value was found
+  // by a null search, this is implemented testing allowNullmove and TT entry type.
 
-  bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply) {
+  bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply, bool allowNullmove) {
 
     Value v = value_from_tt(tte->value(), ply);
 
-    return   (   tte->depth() >= depth
+    return   (allowNullmove || !(tte->type() & VALUE_TYPE_NULL) || !ZugDetection)
+
+          && (   tte->depth() >= depth
               || v >= Max(value_mate_in(PLY_MAX), beta)
               || v < Min(value_mated_in(PLY_MAX), beta))
 
@@ -2769,7 +2774,7 @@ namespace {
         }
 
         // Wait until the thread has finished launching and is gone to sleep
-        while (threads[i].state != THREAD_SLEEPING);
+        while (threads[i].state != THREAD_SLEEPING) {}
     }
   }
 
@@ -2810,7 +2815,7 @@ namespace {
 
     SplitPoint* sp;
 
-    for (sp = threads[threadID].splitPoint; sp && !sp->stopRequest; sp = sp->parent);
+    for (sp = threads[threadID].splitPoint; sp && !sp->stopRequest; sp = sp->parent) {}
     return sp != NULL;
   }